Flash lamp



Oct. 31, 1939.

R. s. MACKIE 2,178,430

FLASH LAMP Filed March 50, 1937 Inventor: Richard S. Mackie,

by M

His Attorney.

Patented Oct. 31, 1939 UNITED STATE-S PATENT OFFICE FLASH LAMP ration ofNew York Application March 30, 1937, Serial No. 133,875

7 Claims.

My invention relates to flash'lamps and more particularly to that typeof flash lamp used for photographic purposes which usually comprises asealed transparent bulb in which is enclosed a readily combustiblematerial, such as metal foil or wire, togetherwith a substance, usuallya gas filling, which, upon ignition, enters into a reaction with thecombustible material with the resulting emission of actinic light.

To initiate the actinic reaction, it is necessary to provide some formof ignition means therefor. The type of ignition means customarilyemployed for such purpose comprises a resistance element or filamentembedded in a bead of ignition paste and supported within the bulb inclose proximity to the combustible material by a conventional mountstructure. The ignition paste generally used is extremely sensitive, andwhen the electrical circuit through the filament is energized, theheated filament promptly ignites the bead of ignition paste which inturn ignites the combustible material, thus initiating the actinicreaction.

As a safeguard against explosion of the glass bulb when a lamp of thistype is flashed, it is customary to test the same for the presence ofair. One desirable method of conducting such a test, known as a coiltest, consists in the use of high frequency equipment employing glowtubes.

It has been found, however, that such a method of testing results in theloss of a great number of flash lamps through the premature flashing ofthe same, termed flash-outs, which is caused by the ignition of theextremely sensitive bead of ignition paste by the high frequency of thetest equipment. In addition, accidental smashing or breaking of a flashlamp may ignite the bead of ignition paste so that the lamp catchesfire. Furthermore, the bead of ignition paste is very fragile, andfrequently cracks or breaks off during shipment or other handling of thelamp. I have accordingly devised a novel form of ignition means orprimer head for flash lamps whichprevents the premature flashing of thesame, eliminates the danger of such lamps catching fire when smashed orbroken, and possesses increased mechanical strength and resistance tocracking and breaking off.

One object of my invention is to provide an 50 improved flash lamp whichwill not flash prematurely when subjected to various external phenomena,such 'as sparks induced by high frequency, corona. or the like.

Another object of my invention is to provide an improved flash lampwhich will not catch flre and burn when accidentally smashed or broken.

Still another object of my invention is the provision of a novel form ofignition means for flash lamps which will not ignite when subjected tovarious external phenomena, such as sparks induced by high frequency,corona, and the like, or when the lamp is smashed or broken.

A further object of my invention is the provision of a coating oflacquer or other similar non-conducting material on the bead of ignition10 paste-of a flash lamp, which coating will exclude such paste fromvarious external phenomena normally tending to ignite it.

A still further object of my invention is the provision of a coating ofnon-conductive ma- 16 terial on the bead of ignition paste of a flashlamp, which coating preferably consists of a lacquer composed of a resinsolution, a nitrocellulose lacquer, land a plasticizer.

Another object of my invention is the pro- 20 vision of a coating ofthermoplastic material on the primer bead of a flash lamp which coatingwill cause metal foil or wire of the lamp to adhere to the head duringthe sealing in operation.

A further object of my invention is the pro- 25 vision of a coating onthe primer bead of a flash lamp which will add mechanical strength tothe' bead and prevent it from cracking and breaking off.

Other objects and advantages of my invention 30 will appear from thefollowing description of species thereof and from the accompanyingdrawing, in which:

Fig. 1 is an elevation ofa flash lamp comprising my invention in whichthe ignition means 5 comprises a bead of ignition paste enclosing thefilament and coated with a layer of thermoplastic non-conductivematerial, and Fig. 2 is an enlarged fragmentary sectional. view of aportion of a bead of ignition paste coated in accord- 40 ance with myinvention.

Referring to Fig. 1, the lamp comprises a vitreous bulb l0 containing asmall filament H, the ends of which are connected to lead-in wires I2,l2 which extend through a stem Hi to the 5 base I 4. The filament II isembedded in a fulminating substance 15 to thereby form the ignitionmeans for the lamp. A disc I 6, preferably of asbestos, is mounted onthe stem I3 to shield the base end of the lamp from the heat ofcombustion. The bulb I0 is loosely filled with combustible material I],consisting of metal foil or wire, usually of aluminum.

The fulminating substances or primer bead l5 customarily employed inflash lamps of the type described above is composed of an extremelysensitive metal powder l8, such as zirconium metal, together with anoxidizing agent, such as lead peroxide, mixed with a suitable binder,such as lacquer. When a head of this paste dries, the metal powderparticles at the surface protrude therefrom, and under the microscopehave the appearance of fuzz. It is this fuzz that causes the head ofignition paste to flash when a slight spark or even corona strikes thesame. Similarly, the friction apt to be exerted on such fuzz when aflash lamp is accidentally smashed or broken might cause the bead ofpaste to flash, with the attendant danger of fire. By covering this fuzzor roughened surface with a coating of a suitable non-conductivesubstance.l9, as shown in Fig. 2, the metal powder I8 is therebyexcluded from the action of all external phenomena thereon tendingtoignite the same, such as sparks induced by high frequency, or corona,friction, and the like. In this manner, the premature flashing of thebead of ignition paste [8, and of the flash lamp itself, during test orwhen broken, is prevented. In addition, the coating i9 definitely adds aconsiderable amount of mechanical strength to the fragile bead ofignition paste, thereby reducing the danger of the bead cracking andbreaking off during shipment and other handling of the lamp.

The coating material l9 may consist of a mixture of a synthetic ornatural resin solution with or without nitrocellulose lacquer and withor without a suitable plasticizer, dissolved in suitable solvents. touse is that commercially known as Glyptal varnish, but the resincontained therein may be any other resin having thermoplasticproperties. The nitrocellulose lacquer may consist of nitrocellulosedissolved in a suitable solvent or solvents, such as acetone, while theplasticizer may be dibutylphthalate, tricresylphosphate, or some othersimilar substance. The above mixture of a resin solution, nitrocelluloselacquer and a plasticizer is diluted with a suitable thinner or diluent,preferably that known as Ault and Wibcrg thinner H8349. The coatingmaterial may be applied to the fulminating substance or primer bead i5by simply dipping such bead in the coating material and allowing thelatter to dry thereon. During this drying process, the aforementionedthinner or diluent evaporates, leaving a coating of solid material onthe fulminating substance consisting of the mixture of a resin solution,nitrocellulose lacquer and a plasticizer referred to above.

The synthetic resin preferably employed in the coating material [9, andcommercially known as Giyptal, possesses the property ofthermoplasticity; or, in other words, it becomes plastic upon theapplication of heat thereto. This resin is present in suflicientquantity in the coating 'material iii to impart this property ofthermoplasticity to the coating material itself, so that the heatattending the sealing of the mount in the bulb renders such coatingmaterial plastic. Any portion of the metal foil or wire I! within thelamp coming into contact with the coating material while the same is insuch a plastic state will permanently adhere to such coating materialand accordingly to the primer bead. thus insuring positive andinstantaneous ignition of the metal foil or wire upon the ignition ofthe primer bead.

The synthetic resin solution I prefer Although the preferred form of theinvention is shown and described herein, it is to be understood thatmodifications may be made therein, such as the use of coatings of acomposition other than those mentioned above, without departing from thespirit and scope of the invention as described herein and as setforth inthe appended claims.

What I claim as new and desire to'secure by Letters Patent of the UnitedStates is:

l. A flash lamp comprising a sealed container,

a quantity of combustible material within said container, and means forigniting said combustible material, said means including a head ofhighly sensitive fulminating substance comprising readily ignitablemetallic powder and coated with a layer of material comprising a mixtureof a thermoplastic resin solution and a nitrocellulose lacquer. 2. Aflash lamp comprising a sealed container. a quantity of combustiblematerial within said container, and means for igniting said combustiblematerial, said means including a bead of highly sensitive fulminatingsubstance comprising readily ignitable metallic powder and coated with alayer of material comprising a mixture of a thermoplastic resin solutionand a plasticizer.

3. A flash lamp comprising a sealed container, a quantity of combustiblematerial within said container, and means for igniting said combustiblematerial, said means including a bead of highly sensitive fulminatingsubstance comprising readily ignitable metallic powder and coated with alayer of material comprising a mixture of a thermoplastic resinsolution, a nitrocellulose lacquer, and a plasticizer.

4. A flash lamp comprising a sealed container, a quantity of combustiblematerial within said container, and means for igniting said combustiblematerial, said means including a bead of highly sensitive fulminatingsubstance comprising readily ignitable metallic powder and coated with alayer of thermoplastic lacquer.

5. A flash lamp comprising a sealed container, a quantity of combustiblematerial within said container, and means for igniting said combustiblemateriahsaid means comprising an electrical translation element embeddedin a bead of highly sensitive fulminating substance comprising readilyignitable metallic powder, said bead being coated with a layer ofthermoplastic lacquer.

6. A flash lamp comprising a sealed container, a quantity of combustiblematerial within said container, and means including a bead of highlysensitive fulminating substance comprising readily ignitable metallicpowder for igniting said combustible material, a portion of saidcombustible materi: being securely attached'to said bead of fulminatingsubstance by a thermoplastic lacquer.

7. A flash lamp comprising a sealed container, a quantity of combustiblematerial within said container, and means for igniting said combustiblematerial including a bead of highly sensitive fulminating substancecomprising readily ignitable metallic powder, said bead having thereon aprotective coating of thermoplastic resinous lacquer of sufficientthickness to prevent ignition of said bead upon breakage of the saidcontainer.

RICHARD S. MACKIIE.

